Law enforcement is frequently confronted with crowds composed of both law-abiding citizens and dangerous criminals. In these situations law enforcement needs to protect itself against those in the crowd wishing to cause harm without harming those who are merely present.
A typical law enforcement response to this situation is to illuminate the crowd with high intensity incandescent spot lights. This response is beneficial; however, it does not effectively degrade the visibility of the criminal element within the crowd. In addition, its effect can be overcome with sunglasses or shielding of the eyes. High intensity lights alone do not do enough to encourage the crowd to disperse.
Some high intensity incandescent lights for crowd control employ spot beams to assure maximum intensity; however, this is problematic for crowd control because the crowd can easily move such that it is not illuminated.
Some high intensity incandescent lights employed for crowd control are on special vehicles because the individual lights require large amounts of power. This limitation creates a logistics problem because the special vehicle is not always at the required location.
Crowds can easily move or shift such that they are no longer illuminated by the incandescent lights. Crowd movement would force law enforcement to reposition the special vehicles in order to maintain illumination; however, repositioning vehicles to follow crowd movement is not practical.
Some high intensity incandescent lights which continuously illuminate or which glow for a period of time after being turned off make it hazardous for law-enforcement within or adjacent to the vehicles because criminal elements within the crowd can shoot at the lights potentially hitting officers within the vicinity of the lights.
Some high-intensity lights are not directional such that they illuminate all persons in the vicinity of a crowd providing equal illumination of the crowd and law-enforcement.
Some high intensity steady lights lose their effectiveness as ambient lighting increases. Hence, within zones having bright street lighting, during dusk or daytime high-intensity lights cannot be relied upon as a method of crowd control.
Some high intensity lights on vehicles cannot be employed to illuminate crowds in locations which do not permit vehicular traffic.
Some high intensity lights emitting only a single color do not adequately degrade the visual acuity of hostile persons within the crowd.
Thus, all above mentioned high intensity lights are defective in effectively protecting police from those within a crowd wishing to do them harm.